Synthesis and Properties of a Thermo-/Light-Sensitive Hydrogel

A newly developed water-soluble azobenzene-containing monomer, 4-(4-((4- ethoxyphenyl)diazenyl)phenoxy)-N-(2-(methacryloyloxy)ethyl)-N,N-dimethylbutan-1-aminium bromide (assigned to M), was synthesized, and then a thermo-/light-sensitive gel was prepared by copolymerization of M and N-isopropylacrylamide. The properties of the gel were subsequently investigated by DSC, UV-vis, and gravimetry. The results showed that the copolymer hydrogel had a very quickly tran-cis photoisomerization rate upon UV irradiation. The critical solution temperature (CST) of the copolymer hydrogel could be toned by the M content and U, did also of the swelling ability.